Updated docker base image

Updated base image from 13.10 (which is almost EOL: July 2014) to 14.04 LTS.
Also fixes ```IO::Socket::SSL 1.84 required for TLS support``` problem (looks like that first appeared after the dependency update in 14ffea10b9c8b64b36687057219b10ca3ba4520f) as it ships newer version of libio-socket-ssl-perl.